Fuel injection pump



pri 19A, H933, F KOVACH @Elli-,5

FUEL INJECTION PUMP Filed July 13, 1935 2 Sheets-Sheet 2 Patented Apr.19, 1938 PATENT GFFICE FUEL INJECTION PUMP Frank Kovach, Lincoln, Nebr.,assignor of one-v half to H. V. Martin, Lincoln, Nebr.

Application July 13, 1935, Serial No. 31,267

4 Claims.

This invention relates to pumps and more particularly to the control ofthe stroke and the speed of the. pistons of reciprocating pumps,especially for oil and Diesel engines.

'I'he primary object of the invention is to provide an extremely simpleand accurate device for precisely controlling the effective stroke ofreciprocating pumps. Incidentally an object of the invention is toreduce the number of parts in such controls to about the same as thatrequired for a fixed output pump.

Another object is to provide an extremely sturdy feed control for fuelinjection pumps particularly for high speed oil and Diesel engines,which control may be varied micrometrically over a full range withoutseriously affecting the timing.

Another object is to combine in one simple unit a device which not onlycontrols the amount of the fuel charge but which also and at the sametime varies the rate of fuel injection and yet approximately maintainsthe timing.

The rate at which the fuel is injected into oil and Diesel engines is ofextreme importance in its effect on smooth running and eiliciency. As iswell known, this rate can be easily controlled for wide open throttle byproperly designing the pump cam but the rate so obtained may be andusually is wrong for the lower range of throttle settings. By myinvention I am able to use the cam designed to give maximum eiliciencyat full throttle for all rangesl of throttle settings. I accomplish thisby providing simple means for displacing the cam shaft from the line ofmotion of the cam follower which acts on the pump piston. The preferredpath of displacement is such that altho the effective stroke isdecreased the rate of fuel injection is increased, thus compensating forany bad effect the fixed cam shape may have at lower throttle openings.

In the drawings:

Figure 1 is a' view of the pump looking at it from the control end.

Figure 2 is a longitudinal vertical section taken on line 2--2 of Figurel.

Figure 3 is a transverse vertical section taken on line 3-3 of Figure 2.

Figures 4, 5, 6 and 'l are diagrams showing the control set respectivelyat full throttle, half throttle, idling and stopped.

Figure 8 is a diagrammatic view showing my improved pump connected to anengine.

The fuel injection pump shown in Figures 1, 2 and 3 used to illustratemy invention consists of a plurality of plungers Il) reciprocablymounted in bores I2 in a cylinder block i4 bolted as at I6 to the top ofa cam shaft and tappet casting or housing i8. Springs 20 keep the baseof the plungers in contact with the adjustable ends of roller tappetunits 22 and thus keep the rollers 24 of these units in contact with thecams 26 on the cam shaft 28 which shaft is mounted in the end walls 30of the cam chamber 3| in the lower part of the casting i8 in a novelmanner to be described farther on. The tappet chamber 32 is providedwith a removable cover 34 to permit inspection and adjustment of thetappet units and piston springs.

Thus far the pump is in general no different from the usual well knownconstant feed, constant stroke pumps of this type. The preferred form ofmy invention is obtained by providing the novel bearing unit 36 whichcarries the f bearings 38 of the cam shaft. The unit consists of twocircular members 40 rigidly secured together as by the bar t2 wherebythey may be turned as one in the circular openings or jour. nals M inthe end Walls 30, or by removal of caps 46 and 4W the unit and cam shaftmay be bodily removed from the casting.

The bearings 38 are eccentrically mounted in the circular members 40whereby, as the unit is turned by means of the lever or, governor arm48, the relation of the cam shaft to the tappet rollers is changed aswill be clearly understood by reference to Figures 4 to 7. This causes achange in the clearance of the piston heads, or, what in effect amountsto the same thing, it causes a change in the effective stroke of thepump since the effective stroke is measured by the distance between thehighest position of the plunger end and the top of the fuel inlet portSil. Each of the inlet ports 50 communicates with a common bore 52 whichmay be provided with a shut-off valve 54 at one end and a connection 55at the other end for connection with a supply pipe not shown. Each pumpoutlet p ort 56 is provided with means 5l for connecting with a conduit58 for carrying the fuel charges to the respective engine cylinders inthe usual manner.

The cam shaft 28 may be driven from the engine crank shaft in any mannerwhich permits unimpeded rotation of the bearing unit 36, the onlyrequirement being that the connections used be positive so that the gearratio between the engine and the cam shaft is maintained. One method ofdriving the cam shaft is shown diagrammatically in Figure 8 in which thecrank shaft 60 of the engine 6i is connected for exam- K,

ple, by a chain $2 to drive a shaft ll of the reduction gear unit 64mounted on the engine. The gear unit is connected to one end of the camshaft 28 thru a relatively long shaft C! with one or more universaljoints 66 and 61. I do ,not wish to be limited to any specific manner ofdriving the pump and give this merely as an example. pump may be.applied to almost any type of oil or Diesel engine and, of course, itsspecific drive will depend upon the design of engine on which it isinstalled.

The operation of the pump control will be easily' understood byreference to Figures 4 to 7. 'I'he arrow 68 shows the direction ofrotation of the cam shaft and the arrow 69 shows the direction ofrotation of the bearing or control unit from a point of full throttle asillustrated in Figure 4 to a point of stop as illustrated in Figure 7.

At full throttle (Figure 4) the cam shaft axis, the bearing unit axisand the piston axes al1/lie in the same plane with the result that theeffective stroke oi' the pump is at a maximum. Now moving the governorarm 48 in the direction of arrow 69 the effective stroke of the pump isdecreased to about half when the arm has moved about 45 (Figure 5) andnearly a minimum when the arm has moved approximately 60 (Figure 6) andfinally to zero as the arm reaches between 70 and 80 depending on thedesign of the parts. Incidentally it will be ,apparent to those skilledin the art that the governor arm 48 may be connected to be moved by theengine governor or by a foot or hand throttle lever or by a combinationof these as desired.

Astudy of Figures 4 to 'I will show that three objects result from myextremely simple control.

First, I regulate the quantity of the fuel charge injected per stroke.Second, I regulate the rate of the injection of each fuel charge and,third,

I substantially maintain the timing of the injections. The regulation ofthe quantity or size of the fuel charge will be obvious but theregulation of the rate of injection and the approximate maintenance ofthe timing are not easily appreciated and will therefore be explained.

To illustrate, let us assume the quantity lof fuel injected into theengine at full throttle, i. e., at maximum effective stroke (Figure 4)to be, for example, three drops. Assume further that the cam is soshaped that the rst drop is injected in ten degrees of cam shaftrotation, the second in ten degrees of rotation and the last drop in tendegrees of rotation, under which condition the rate of injection isconstant. Now assume that the cam is dropped in a straight line (so asnot to move out of the center line 1I of the tappet, Figure 4) until theeffective stroke is onethird that at full throttle, i. e., the pump willinject orie drop per stroke. Altho the size of the charge has beenreduced the rate of injection has not been changed since the entireeective stroke will take place in the last 10 of cam shaft rotationexactly the same as the last third of the effective stroke at fullthrottle. The rate of injection, namely,.ten degrees per drop, has notbeen changed by the vertical displacement of the cam shaft in thestraight line 1I. Since the pump piston stroke per degree of cam shaftrotation has not been affected through the throttle range, the rate offuel injection remains constant and depends solely upon the shape of thecam.

A substantially vertical movement oi. the cam shaft could be obtained bylocating the axis of It will be quite obvious that my improved f thebearing unit laterally of and in a plane normal to the piston axis atone-half throttle.

Now instead of dropping the cam shaft straight down assume it to bemoved in a lateral path, such. for example, as the arcuate path 12,Figures 4 to 7, and in the direction indicated by the arrow 69, untilthe effective stroke is one-third maximum at which point the charge isone drop. From a study of the cam action it will be apparent that thespeed of the pump piston per degree of cam shaft rotation is appreciablyincreased by the lateral displacement of the cam shaft from the centerline of thev tappet. 'I'hus f` the slower the engine turns over, due todecrease in fuel charge, the faster the reduced charge is injected infewer degrees of cam shaft rotation than one drop of the maximum charge.

'Ihe timing loss due to the dropping of the cam shaft is partlycompensated for by the cam being displaced laterally from the centerline of the tappet, which makes the cam engage the roller as manydegrees sooner as was lost by the effective plunger stroke due to thedrop of the cam shaft.

Thus it will be seen that by my invention I have provided an extremelysimple control for simultaneously reducing the fuel charge andincreasing the rate `of fuel injection while at the same timemaintaining the timing not far from constant. It will also be seen thatI eliminate the usual series of gears and levers and that all theelements employed such as bearings and bearing supports are solids ofrotation thus not only reducing the cost of production to a minimum butalso reducing the possibility of non-uniform wear and making possiblevery accurate machining, setting and adjustment.

The eccentric mounting of the cam shaft bearings in a rotatable bearingunit is the preferred embodiment of my invention but I do not wish to belimited to this specific construction since a little study will showthat the invention in its broadest aspects may be carried out in aninfinite number of Ways as, for example, replacing the arcuate path 'l2by a path of any desired shape including straight lines (inniteeccentricity) at any desired angle to the line of motion of the tappet.It will also be apparent to those skilled kin this art that for anygiven engine the design of the cam will depend on the shape anddirection of the path of cam shaft displacement chosen. Or for any givencam and engine the choice of the path of displacement will depend uponthe kind of engine operation that may Y be desired.

What I claim is:

1. Afuel pump for Diesel engines comprising a housing having a cam shaftchamber and a tappet chamber above the cam shaft chamber, a horizontalwall between said chambers having vertical bores, a plurality of tappetsin said bores and having adjustable upper ends, the upper wall for saidtappet chamber having bores arranged coaxially of said tappet bores, acylinder block removably but tlxedly secured to said housing and havingcylinder bores located coaxially of said coaxially arranged bores, saidcylinder bores having fuel inlet and outlet ports, pistons in saidcylinder bores acting as slide valves to control said inlet ports andprojecting into the tappet chamber for engaging the adjustable upperends of said tappets, springs around the respective pistons formaintaining said engagement, said cam shaft chamber having a pair ofalined bores in the end walls. bearing supports rotatably mounted in thealined bores, bearings eccentrically lcarried in the supports, meanswithin the chamber rigidly connecting said supports together formaintaining the bearings in coaxial relation and for .rotating thesupports as a unit, a cam shaft in said bearings and having cams forengaging the tappets, means for preventing axial movement of the camshaft, said preventing means being removable for permitting the removaland insertion of the supports and cam shaft as a single unit, saidtappet chamber having a removable side wall for permitting access toadjust said tappets and for moving the tappets to clear the cams duringthe insertion or removal of said cam shaft unit.

2. A fuel pump for Diesel engines comprising a housing having a wallseparating the interior intoa cam shaft chamber and a tappet chamber,said wall having tappet bores therein, a plurality of tappets in saidbores, a cylinder block xedly secured to said housing and havingcylinder bores located coaxially of said tappet bores, said cylinderbores having fuel inlet and outlet ports, pistons in said cylinder boresacting as slide valves to control said inlet ports, and projecting intothe tappet chamber for operatively engaging said tappets, springs4associated with the respective pistons for maintaining said engagement,said cam shaft chamber having a pair of alined bores in the"end walls,bearing supports rotatably mounted in said alined bores, bearingseccentrically carried in the supports, means rigidly connecting saidsupports together for maintaining the bearings in coaxial relation 'Xx'and providing for rotation of the supports as a unit, a cam shaft insaid bearings and having cams operatively engaging the tappets, andmeans preventing axial movement of said unit, said preventing meansbeing removable for permitting the removal and insertion of saidsupports with the cam shaft through one of said alined bores as a singleunit.

3. A fuel pump for Diesel engines comprising a housing having ahorizontal wall separating the interior into a cam vshaft chamber and atappet chamber, said wall having vertical tappet bores therein, aplurality of tappets in said bores, a cylinder block removably butilxedly secured to said housing and having cyllnderbores locatedcoaxially of said tappetbores, said cylinder bores having fuel inlet andoutlet ports, spring pressed pistons in said cylinder bores acting asslide valves to control said inlet ports, and projecting into the tappetchamber for operatively engaging said tappets, said cam shaft chamberhaving a pair of alined bores in the end walls, bearing supportsrotatably mounted in said alined bores, bearings eccentrically carriedin the supports, means rigidly connecting said supports together formaintaining the bearings in coaxial relation and for rotating thesupports as a unit, a cam shaft in said bearings and having camsoperatively engaging the tappets, and means preventing axial movement ofsaid supports and the cam shaft carried thereby, said preventing meansbeing removable for permitting the removal and insertion of saidsupports and cam shaft through either one of said alined bores as asingle unit. 4. A fuel injection pump for oil engines comprising acylinder block having a pump bore and a cam chamber, said bore havingfuel inlet and outlet ports, rigidly connected bearing supportsrotatably mounted in two opposite walls of said chamber, bearingseccentrically mounted in said supports, a cam shaft carried in saidbearings,

a cam on said shaft, a piston in said bore opera'tively associated withsaid cam, and acting as a slide valve for said fuel inlet port, said camshaft, shaft bearings and bearing supports being inclosed in saidchamber thereby being free from dust and dirt, said cam shaft beingpositioned between the piston and the support axis at maximum e'ectivestroke, vvwhereby when the cam shaft is in said maximum stroke positionthe cam shaft axis and support axis are both intersected by an extensionof the piston axis, and means connected to said bearing supports forrotating lsaid supports any desired number of degrees in a predeterminedrange of approximately 75 from said maximum effective stroke position,so that as the cam shaft starts toshift from said position its motion issubstantially all lateral and its vertical component of motion issubstantially zero but as the shaft approaches its no load position atthe end o! said range of 75 its lateral component of motion is ofnegligible value while said vertical component approaches the value thelateral component had at maximum effective stroke position.

' FRANK KOVACH.

